The role of one-and two-electron reductions of mitomycin C on its alkylating properties was studied. One-electron reduction is sufficient to unmask drug alkylating activity while two-electron generates a different set of products. The primary mitomycin C metabolites are also reductively activated by NADPH cytochrome P450 reductase and xanthine oxidase. Whole cell reduction of AZQ to free radical anions in human K562 and HL60 and mouse L1210 cell lines was demonstrated. The penetration of AZQ and metabolites into puppy CNS and brain tumor tissue was quantified.